The present invention relates in general to a table assembly adapted to modify a workpiece, and more particularly, to a table assembly adapted to place at least one bend along a length of a stator coil strand used in a turbine generator within a power generation plant.
Many power generation plants produce electricity by converting energy (e.g. fossil fuel, nuclear fission, hydraulic head, geothermal heat) into mechanical energy (e.g. rotation of a turbine shaft), and then converting the mechanical energy into electrical energy (e.g. by the principles of electromagnetic induction). These power generation plants typically use a turbine to convert the energy into mechanical energy and a generator to convert the mechanical energy into electrical energy.
One aspect of the above-described power generation scheme involves conductive coils located within longitudinally extending slots of the generator""s laminated stator core. Each coil typically comprises a plurality of conductive strands that are transposed along their longitudinal length so that each strand experiences a similar amount of flux within the slots and thus carries a similar amount of electric current.
To transpose the strands, at least one bend is typically placed in each strand. The bent strands are then intermingled to form the stator coil having a certain transposition pattern. Exemplary stator coil transposition patterns are described in U.S. Pat. No. 1,144,252 to Roebel and U.S. Pat. No. 5,323,079 to Nieves, et al.
Placing the bends(s) in the strands, however, is a labor intensive, physically demanding, time consuming, precise and expensive process because, among other reasons, the bend(s) are typically placed at different positions along the longitudinal length of each strand, the bend(s) may have different geometries, and the bends may have different amounts of spacing relative to adjacent bends on that or other strands.
There is thus a need for an apparatus and method to simplify the stator coil manufacturing process and, in particular, to simplify the placement of bends in conductive strands forming a stator coil. There is also a need to decrease the amount of time and labor required to make the coil, and to decrease the amount of manual physical exertion and precision required when making the coil. There is also a need for a table assembly that can impress a configuration, design or form upon a workpiece.
One aspect of the present invention thus involves a workpiece table assembly comprising: a table having a surface adapted to support at least one workpiece; a saddle adapted to be movable between a first position and a second position, the first position having at least a portion of the saddle recessed below the surface of the table and the second position having at least a portion of the saddle raised above the surface of the table, the saddle further adapted to hold the workpiece; a die adapted to apply a pressure onto the workpiece sufficient to modify the workpiece; and a step-off board having at least one workpeice portion holder positioned at a desired location along the step-off board, each workpiece portion holder sized and configured to at least partially accept a portion of the workpiece and position the workpiece on the table.
Another aspect of the present invention involves a method of modifying a plurality of offset workpieces, comprising: placing a plurality of workpieces on a surface; arranging a step-off board comprising a protrusion adapted to mate with a depression in the surface to engage the step-off board with the surface, the step-off board further comprising a plurality of workpiece portion holders with each workpiece portion holder adapted to at least partially accept a portion of a workpiece and offset the workpiece relative to the other workpieces; and applying a force onto a die operatively engaged with the offset workpieces, the force sufficient to impress the modification onto the offset workpieces.
Another aspect of the present invention involves method of bending a plurality of copper strands for use in a stator coil used in a turbine generator within a power generation plant, comprising: placing a plurality of copper strands on a surface; arranging a step-off board near the surface, the step-off board having a plurality of notches, each notch adapted to at least partially accept an end of the coil and stagger the coil relative to the other coils; and bending the strands by applying a force onto a die operatively engaged with the offset coils.
Further aspects, features and advantages of the present invention will become apparent from the drawings and detailed description of the preferred embodiments that follow.